Genotypic variation in zinc efficiency and resistance to crown rot disease (Fusarium graminearum Schw. Group 1) in wheat.

摘要

A crown rot disease in wheat caused by Fusarium graminearum [Gibberella zeae] is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency has been established. A test of a further hypothesis, thatwheat genotypes more efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen is reported. Wheat cv. Excalibur, Songlen and durum wheat cv. Durati of differential Zn efficiency were supplied with 0.05, 0.5 or 2.0mg Zn kg-1 of soil and three levels of F. graminearum inoculum (0.1 g and 0.3 g kg-1 live chaff-inoculum and control having 0.1 g kg-1 dead chaff inoculum). Six weeks after sowing, plant growth was decreased by inoculation with 0.05 mg F. graminearum and application of 0.5 mg Zn. 0.1 g F. graminearum inoculum was as effective as 0.3 g kg-1 for infection and decreasing plant dry matter. The infection at the basal part of culm was decreased significantly by increasing the rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and root dry matter, and showed less disease infection compared with the Zn-inefficient cultivars Durati and Songlen at low (0.05 mg) and medium (0.5 mg) Zn rates. The application of 2.0 mg Zn reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating its high Zn requirement and/or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was able to scavenge enough Zn from Zn-deficient soil, suggesting that besides sustaining growth Excalibur was able to build and maintain resistance to the pathogen; inefficient cultivars needed extra Zn to achieve performance comparableto that of Excalibur. It is concluded that growing Zn-efficient cultivars of wheat along with judicious use of Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of the disease as well as by increasing the plant vigour through improved Zn nutrition.